1. Field of the Invention
The present invention relates to reciprocating power tools, and more particularly, to a improvement for retaining the piston in the barrel of a pneumatic tool.
2. Description of the Prior Art
Reciprocating power tools that hammer, chisel, and drill have been utilized in the construction industry for years, and will likely continue to play an important role on most job sites in the future. Pneumatically driven reciprocating tools have proven to be particularly effective in delivering high performance for relatively low cost. While ongoing design improvements have enhanced certain functional aspects of such tools, the basic design concept of a reciprocating pneumatic tool has not changed.
An example of such a tool is the Chicago Pneumatic.TM. 4181.TM. "Rivet Buster." Like most similar pneumatically driven tools, the 4181 includes an elongated barrel with a handle and trigger at one end and a retaining sleeve at the other end for holding a workpiece (e.g., a chisel or the like). Inside an upper portion of the barrel, proximate the handle, is a piston that reciprocates back and forth within the barrel, repeatedly striking the butt end of the workpiece within the lower portion of the barrel, thereby causing the workpiece head to reciprocate outside of the barrel.
As noted above, such tools include a retaining sleeve, which may be removed to perform routine maintenance on the tool or to remove or replace the workpiece. Unfortunately, in tool designs like the 4181, once the sleeve is removed, the piston can freely escape from the barrel. This typically is not seen as a problem given that easy removal of the piston may be desirable for maintenance purposes. Moreover, as long as the user takes basic precautionary steps, such as disengaging the tool from the air supply before removing the sleeve, the design presents no problem. However, if the worker fails to take such precautions, the piston could inadvertently exit the barrel. For example, if the sleeve is removed and the trigger is pressed while the tool is operable, the piston could be ejected from the barrel with a fair amount of force, causing damage to the piston.
Thus, a need exists to provide a mechanism that can be readily incorporated into existing tools that will prevent the free escape of the piston from the barrel when the retainer sleeve is removed. In addition, the mechanism should be easily replaceable, and be located where it does not interfere with the existing functionality of the tool.